"Becky Stern and Phil Torrone from Adafruit test out Rust-oleum's NeverWet two-part spray-on hydrophobic coating on DIY electronics including the FLORA Citi Bike Helmet under the hose, an underwater Raspberry Pi, Arduino Micro and more." Their testing shows that NeverWet works, but there are some caveats. NeverWet degrades in the sun and when dried, leaves a chalky coating that can rub off onto your hands.